[Core & Milky] Implement GroupFileEntity and file Segment (#65)

Author: Wesley-Young

Lagrange.Core/Internal/Packets/Message/Elem.cs

@@ -9,6 +9,8 @@ internal partial class Elem
     [ProtoMember(1)] public Text? Text { get; set; } 
 
     [ProtoMember(4)] public NotOnlineImage? NotOnlineImage { get; set; }
+
+    [ProtoMember(5)] public TransElem? TransElemInfo { get; set; }
 
     [ProtoMember(8)] public CustomFace? CustomFace { get; set; }
 
@@ -101,6 +103,14 @@ internal partial class NotOnlineImage
     [ProtoMember(29)] public byte[] PbReserve { get; set; }
 }
 
+[ProtoPackable]
+internal partial class TransElem
+{
+    [ProtoMember(1)] public uint ElemType { get; set; }
+
+    [ProtoMember(2)] public byte[] ElemValue { get; set; }
+}
+
 [ProtoPackable]
 internal partial class CustomFace
 {

Lagrange.Core/Internal/Packets/Message/Extra.cs

@@ -53,4 +53,40 @@ internal partial class SourceMsgResvAttr
     [ProtoMember(6)] public string SenderUid { get; set; }
 
     [ProtoMember(7)] public string ReceiverUid { get; set; }
+}
+
+[ProtoPackable]
+internal partial class GroupFileExtra
+{
+    [ProtoMember(1)] public uint Field1 { get; set; }
+    
+    [ProtoMember(2)] public string FileName { get; set; }
+    
+    [ProtoMember(3)] public string Display { get; set; }
+    
+    [ProtoMember(7)] public GroupFileExtraInner Inner { get; set; }
+}
+
+[ProtoPackable]
+internal partial class GroupFileExtraInner
+{
+    [ProtoMember(2)] public GroupFileExtraInfo Info { get; set; }
+}
+
+[ProtoPackable]
+internal partial class GroupFileExtraInfo
+{
+    [ProtoMember(1)] public uint BusId { get; set; }
+    
+    [ProtoMember(2)] public string FileId { get; set; }
+    
+    [ProtoMember(3)] public long FileSize { get; set; }
+    
+    [ProtoMember(4)] public string FileName { get; set; }
+    
+    [ProtoMember(5)] public uint Field5 { get; set; }
+    
+    [ProtoMember(7)] public string Field7 { get; set; }
+
+    [ProtoMember(8)] public string FileMd5 { get; set; }  // hexed
 }

Lagrange.Core/Message/Entities/GroupFileEntity.cs

@@ -0,0 +1,48 @@
+using Lagrange.Core.Internal.Packets.Message;
+using Lagrange.Core.Utility;
+using Lagrange.Core.Utility.Binary;
+
+namespace Lagrange.Core.Message.Entities;
+
+public class GroupFileEntity : IMessageEntity
+{
+    public string FileId { get; internal init; } = string.Empty;
+
+    public string FileName { get; internal init; } = string.Empty;
+
+    public long FileSize { get; internal init; }
+
+    public byte[] FileMd5 { get; internal init; } = [];
+
+    public string FileUrl { get; set; }  = string.Empty;
+
+    public Task Postprocess(BotContext context, BotMessage message)
+    {
+        return Task.CompletedTask; // TODO: implement group file download event
+    }
+
+    Elem[] IMessageEntity.Build() => throw new NotSupportedException();
+
+    IMessageEntity? IMessageEntity.Parse(List<Elem> elements, Elem target)
+    {
+        if (target.TransElemInfo is { ElemType: 24 } trans)
+        {
+            var payload = new BinaryPacket(trans.ElemValue.AsSpan());
+            payload.Skip(1);
+            var data = payload.ReadBytes(Prefix.Int16 | Prefix.LengthOnly);
+            var extra = ProtoHelper.Deserialize<GroupFileExtra>(data).Inner.Info;
+
+            return new GroupFileEntity
+            {
+                FileId = extra.FileId,
+                FileName = extra.FileName,
+                FileSize = extra.FileSize,
+                FileMd5 = Convert.FromHexString(extra.FileMd5)
+            };
+        }
+
+        return null;
+    }
+
+    public string ToPreviewString() => $"[群文件 {FileName}]";
+}

Lagrange.Milky/Entity/Segment/FileSegment.cs

@@ -0,0 +1,26 @@
+using System.Text.Json.Serialization;
+
+namespace Lagrange.Milky.Entity.Segment;
+
+[method: JsonConstructor]
+public class FileIncomingSegment(FileIncomingSegmentData data) : IncomingSegmentBase<FileIncomingSegmentData>(data)
+{
+    public FileIncomingSegment(string fileId, string fileName, long fileSize) : this(new FileIncomingSegmentData(fileId, fileName, fileSize, null)) { }
+
+    public FileIncomingSegment(string fileId, string fileName, long fileSize, string fileHash) : this(new FileIncomingSegmentData(fileId, fileName, fileSize, fileHash)) { }
+}
+
+public class FileIncomingSegmentData(string fileId, string fileName, long fileSize, string? fileHash)
+{
+    [JsonPropertyName("file_id")]
+    public string FileId { get; } = fileId;
+
+    [JsonPropertyName("file_name")]
+    public string FileName { get; } = fileName;
+
+    [JsonPropertyName("file_size")]
+    public long FileSize { get; } = fileSize;
+
+    [JsonPropertyName("file_hash")]
+    public string? FileHash { get; } = fileHash;
+}

Lagrange.Milky/Utility/EntityConvert.Segment.cs

@@ -70,6 +70,7 @@ public async Task<MessageChain> FakeSegmentsAsync(IReadOnlyList<IOutgoingSegment
             (int)video.VideoSize.Y,
             (int)video.VideoLength
         ),
+        GroupFileEntity groupFile => new FileIncomingSegment(groupFile.FileId, groupFile.FileName, groupFile.FileSize),
         MultiMsgEntity multiMsg => new ForwardIncomingSegment(multiMsg.ResId!),
         LightAppEntity lightApp => new LightAppIncomingSegment(lightApp.AppName, lightApp.Payload),
         // ? => new MarketFaceSegment(...),